Is There a Difference in These Training Ideas?

Is there any physical advantages over the other by doing either;

2 X 20 min high intensity full body circuits (one at am, one at pm), every second day


1 X 20 min high intensity full body circuits, everyday?

I think the difference would be negligible. Doing 1 x 20 mins everyday might give you slightly better results as it would give your metabolism a boost daily and 7 single bouts a week may add up to more (EPOC) than 2 bouts x 3 days. However, if you have a large training volume and are struggling with recovery all the time you might be better off giving yourself some complete rest days.